The present invention relates to a precision product container comprising a polycarbonate resin composition as a base material, and more particularly, to a precision product container for containing (inclusive of transporting, storing, and transferring between respective steps) precision products such as electrical parts or electronic parts which tend to be severely damaged even by a trace amount of impurities or contaminants (e.g., various wafers for semiconductors such as unprocessed wafers, discrete wafers, semi-processed wafers before being finished into circuits, patterned wafers, dicing wafers or the like; semiconductor materials such as IC chips or the like; various masks such as photo masks or the like; lead frames; disc substrates such as aluminum discs or the like; various display devices such as liquid crystal panels or plasma display panels; or the like).
Polycarbonate resin containers have been widely used, because these containers are transparent or translucent so that the contents to be contained are visible from outside, and can exhibit excellent properties such as impact resistance. In recent years, kinds of products to be contained in such containers tend to spread widely, so that these containers have been applied to the field of precision products which are required to be strictly free from contamination, such as electrical parts or electronic parts or devices.
However, in certain kinds of precision products such as wafers or semiconductor materials such as IC chips, because of high performance thereof, the precision products which are contained in these containers, sometimes suffer from operational errors when subsequently assembled or processed.
As a result of the analysis of these errors, it has been recognized that chlorine (Cl) ions volatilized from the polycarbonate resin container adversely affect the performance of the precision products to be contained.
In Japanese Patent Application Laid-Open Nos. 62-297320(1987) and 62-297321(1987) which are directed to a method of reducing the amount of chlorine in order to prevent the corrosion of a metal mold used upon molding the polycarbonate resin, it has been described that since phosgene contains as impurities carbon tetrachloride having a boiling point higher than that of phosgene, the content of carbon tetrachloride in phosgene is to be reduced to not more than a predetermined amount in order to prevent the generation of hydrogen chloride by heating upon molding the polycarbonate resin.
On the other hand, there have been hitherto reported many polycarbonate resins to which an epoxy compound is added. For example, in Japanese Patent Application Laid-Open (KOKAI) Nos. (1979), 56-88459(1981), 56-32228(1981), 57-37174(1982) and 58-17224(1983), it has been described that an epoxy compound is added together with various heat stabilizers in order to enhance a heat stability of polycarbonate resins. Further, in Japanese Patent Application Laid-Open (KOKAI) No. 52-104564(1977) and Japanese Patent Publication (KOKOKU) No. 60-17224(1985), it has been described that a halogen-containing compound and an epoxy compound coexist in polycarbonate resins. Therefore, the addition of an epoxy compound to polycarbonate resins is widely known in the arts. In addition, in the case of fire-retardant polycarbonate resin composition containing a halogen-containing compound, it is known that an epoxy compound is used for capturing halogen atoms which are expected to be generated from the heat-unstable halogen-containing compound.
However, it has never been known to use the above-mentioned resin compositions for precision product containers. The reason therefor is as follows. That is, there has been a predominant tendency that the content of impurities which are expected to be generated from precision product containers, is reduced to a level as small as possible, so that the addition of additives such as the epoxy compound to the precision product containers has been avoided.
As a result of the present inventors"" earnest studies concerning chlorine (Cl) contained in polycarbonate resin molded products, it has been found that by using a polycarbonate resin composition into which an epoxy compound having a functional group capable of capturing chlorine is kneaded in an amount corresponding to the content of chlorine therein, there can be obtained a precision product container in which the chlorine normally volatilized can be retained in polycarbonate resin composition without being volatilized therefrom, and the epoxy compound added does not adversely affect products contained therein.
More specifically, it has been found that in the case where carbon tetrachloride remains in the polycarbonate resin or in the case where a chloroformate group produced in the course of the polycarbonate resin production process according to a two-phase interfacial method still remains in the polycarbonate resin, there tends to be caused such a phenomenon that hydrogen chloride (HCl) is generated upon melt-molding of the polycarbonate resin; or that when a specific portion of diphenols is chlorinated in any form by chlorine which remains as an impurity in phosgene during the reaction of an aqueous solution of diphenol alkali metal salt with phosgene at an initial stage of the polycarbonate resin production process, and the chlorinated portions remains unchanged up to the final step, chlorine is gradually volatilized from the resultant polycarbonate resin molded product while allowing the product to stand in an ambient condition (in this case, the chlorine is detected in the form of chlorine ions), but the phenomenon of volatilizing chlorine in any form from the polycarbonate resin can be inhibited by adding thereto an epoxy compound in an amount corresponding to those of these chlorine compounds. The present invention has been achieved on the basis of these findings.
It is an object of the present invention to provide a container for a precision product which is free from operational errors of the precision product contained therein when this product is subsequently assembled or processed.
In a first aspect of the present invention, there is provided a precision product container comprising a resin composition as a base material, which comprises a polycarbonate resin and an epoxy compound.
In a second aspect of the present invention, there is provided a precision product container comprising a resin composition as a base material, which comprises a polycarbonate resin and an epoxy compound,
the amount of chlorine (Cl) ions volatilized from the resin composition to a gas phase within a glass tube, being not more than 15 ppb when the resin composition previously dried until the percentage of water absorption thereof reaches not more than 0.05% by weight, is charged in the glass tube, and the glass tube is sealed under a pressure of not more than 1 mmHg heated to 280xc2x0 C. for 30 minutes, cooled to 23xc2x0 C. and then allowed to stand at an ordinary temperature (23xc2x0 C.) for 3 days.
In a third aspect of the present invention, there is provided a precision product container comprising a resin composition as a base material which contains a polycarbonate resin and an epoxy compound,
the amount of chlorine (Cl) ions volatilized from the polycarbonate resin to a gas phase within a glass tube, being not more than 30 ppb when the polycarbonate resin previously dried until the percentage of water absorption thereof reaches not more than 0.05% by weight, is charged in the glass tube, and the glass tube is sealed under a pressure of not more than 1 mmHg, heated to 280xc2x0 C. for 30 minutes, cooled to 23xc2x0 C. and then allowed to stand at an ordinary temperature (23xc2x0 C.) for 3 days,
and the amount of the epoxy compound being 1 ppm to 1,000 ppm.
Thus, by using a polycarbonate resin composition which contains an epoxy compound and inhibits the volatilization of chlorine therefrom as a base material for a precision product container (hereinafter referred to merely as xe2x80x9ccontainerxe2x80x9d), it is possible to prevent precision products contained in the container from being contaminated by halogen impurities and additives.